This invention has relation to heat transfer units in which a water bath in a vaporizer chamber is used to pick up heat from an elongated direct fired combustion chamber extending horizontally from end to end through the vaporizer chamber and from a plurality of flues carrying the products of combustion from the combustion chamber back, end to end, horizontally through the vaporizer chamber; and to transmit that heat to heat transfer coils extending horizontally through the vaporizer chamber.
These units can be used to transfer the heat to any kind of a fluid passing through the heat transfer coils, but in the present illustration, the heat is used to vaporize liquid propane.
Much greater heat transfer efficiency can be obtained in such a system where it is possible to cause the water bath to circulate between the area where the heat is being received into the water bath from the direct fired combustion chamber and flues and the area where the heat is being delivered from that bath to the heat transfer coils. Before the present invention, however, without special pumps operating on and/or in the water bath itself, the best circulation that could be obtained was a straight up bubbling or boiling kind of action due to the intense heat below and the uniform cooling effect of the coils above.
By using such pumps in the water bath to circulate the water of the water bath, better heat transfer characteristics were obtained. However, such pumps must operate at the elevated water bath temperatures and so are subject to high maintenance needs, use additional (otherwise wasted) power and are particularly difficult or impossible to maintain in service at least without shutting down the heat transfer unit.
In order to develop an automatic natural pattern of circulation of the water in the water bath, the present invention was developed.
No preliminary search of the prior art has been made.